mm/filemap: add filemap_range_uptodate

Move the complicated condition and the calculations out of
filemap_update_page() into its own function.

[willy@infradead.org: unlock page before dropping its refcount]
Link: https://lkml.kernel.org/r/20210201125229.GO308988@casper.infradead.org
Link: https://lkml.kernel.org/r/20210122160140.223228-14-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Kent Overstreet <kent.overstreet@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/filemap.c b/mm/filemap.c
index cd863c4..1eaafc9 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2233,11 +2233,36 @@ static int filemap_read_page(struct file *file, struct address_space *mapping,
        return error;
 }
 
+static bool filemap_range_uptodate(struct address_space *mapping,
+               loff_t pos, struct iov_iter *iter, struct page *page)
+{
+       int count;
+
+       if (PageUptodate(page))
+               return true;
+       /* pipes can't handle partially uptodate pages */
+       if (iov_iter_is_pipe(iter))
+               return false;
+       if (!mapping->a_ops->is_partially_uptodate)
+               return false;
+       if (mapping->host->i_blkbits >= (PAGE_SHIFT + thp_order(page)))
+               return false;
+
+       count = iter->count;
+       if (page_offset(page) > pos) {
+               count -= page_offset(page) - pos;
+               pos = 0;
+       } else {
+               pos -= page_offset(page);
+       }
+
+       return mapping->a_ops->is_partially_uptodate(page, pos, count);
+}
+
 static int filemap_update_page(struct kiocb *iocb,
                struct address_space *mapping, struct iov_iter *iter,
-               struct page *page, loff_t pos, loff_t count)
+               struct page *page)
 {
-       struct inode *inode = mapping->host;
        int error;
 
        if (!trylock_page(page)) {
@@ -2254,26 +2279,15 @@ static int filemap_update_page(struct kiocb *iocb,
 
        if (!page->mapping)
                goto truncated;
-       if (PageUptodate(page))
-               goto uptodate;
-       if (inode->i_blkbits == PAGE_SHIFT ||
-                       !mapping->a_ops->is_partially_uptodate)
-               goto readpage;
-       /* pipes can't handle partially uptodate pages */
-       if (unlikely(iov_iter_is_pipe(iter)))
-               goto readpage;
-       if (!mapping->a_ops->is_partially_uptodate(page,
-                               pos & (thp_size(page) - 1), count))
-               goto readpage;
-uptodate:
-       unlock_page(page);
-       return 0;
 
-readpage:
-       if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ)) {
-               unlock_page(page);
-               return -EAGAIN;
-       }
+       error = 0;
+       if (filemap_range_uptodate(mapping, iocb->ki_pos, iter, page))
+               goto unlock;
+
+       error = -EAGAIN;
+       if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ))
+               goto unlock;
+
        error = filemap_read_page(iocb->ki_filp, mapping, page);
        if (error == AOP_TRUNCATED_PAGE)
                put_page(page);
@@ -2282,6 +2296,9 @@ truncated:
        unlock_page(page);
        put_page(page);
        return AOP_TRUNCATED_PAGE;
+unlock:
+       unlock_page(page);
+       return error;
 }
 
 static int filemap_create_page(struct file *file,
@@ -2351,9 +2368,6 @@ got_pages:
        {
                struct page *page = pvec->pages[pvec->nr - 1];
                pgoff_t pg_index = page->index;
-               loff_t pg_pos = max(iocb->ki_pos,
-                                   (loff_t) pg_index << PAGE_SHIFT);
-               loff_t pg_count = iocb->ki_pos + iter->count - pg_pos;
 
                if (PageReadahead(page)) {
                        if (iocb->ki_flags & IOCB_NOIO) {
@@ -2370,8 +2384,7 @@ got_pages:
                        if ((iocb->ki_flags & IOCB_WAITQ) &&
                            pagevec_count(pvec) > 1)
                                iocb->ki_flags |= IOCB_NOWAIT;
-                       err = filemap_update_page(iocb, mapping, iter, page,
-                                       pg_pos, pg_count);
+                       err = filemap_update_page(iocb, mapping, iter, page);
                        if (err) {
                                if (err < 0)
                                        put_page(page);